Two fair dice (with faces labeled 1, 2, 3, 4, 5, and 6) are rolled.Let the random variable X denote the sum of the outcomes obtained.The expectation of X is ___...

A fair die with faces {1, 2, 3, 4, 5, 6} is thrown repeatedly till '3' is observed for the first time. Let X denote the number of times the die is thrown. The e...

The variance of the random variable X with probability density function f(x) = (1/2)|x|e-|x| is __________.